Hello,
I am building a pergola with a corrugated plastic roof and have some questions about how to solve the roof part.
The floor (decking) is almost finished and I have 2 posts on which one side of the floor (and later the roof) will rest.
The other side will rest on a beam attached to an existing building.
There is about 3 m between the posts and about 3 meters from the posts to the wall, thus roughly a square of 3x3 m.
The problem with the roof is that it is quite low, partly because the roof of the building the pergola is to be attached to is quite low (about 2.25 from the decking), but also because there is a wind board (name?) of about 10 cm which I want to place under the corrugated plastic. This means that the "top" of the roof should not be higher than 2.15m.
Traditionally, one would have placed a beam (45x145?) on the posts and then placed the rafters (45x145?) on top of that, but then the beam would be 2.25 - 0.1 - 0.145 - 0.145 = 1.86 m and it would be a bit in the way when walking under it.
So I would like to see the entire roof framework, including the beam, be 145 thick.
I see 2 alternatives where the beam can be at the higher height and would like to know what you think of them, or if it can be solved in any other way.
Would 45x120 be sufficient as rafters?
If not, would it be enough with double 45x120 glued together?
I hope I make myself reasonably understood, otherwise, just let me know!
Best regards,
Christian
I am building a pergola with a corrugated plastic roof and have some questions about how to solve the roof part.
The floor (decking) is almost finished and I have 2 posts on which one side of the floor (and later the roof) will rest.
The other side will rest on a beam attached to an existing building.
There is about 3 m between the posts and about 3 meters from the posts to the wall, thus roughly a square of 3x3 m.
The problem with the roof is that it is quite low, partly because the roof of the building the pergola is to be attached to is quite low (about 2.25 from the decking), but also because there is a wind board (name?) of about 10 cm which I want to place under the corrugated plastic. This means that the "top" of the roof should not be higher than 2.15m.
Traditionally, one would have placed a beam (45x145?) on the posts and then placed the rafters (45x145?) on top of that, but then the beam would be 2.25 - 0.1 - 0.145 - 0.145 = 1.86 m and it would be a bit in the way when walking under it.
So I would like to see the entire roof framework, including the beam, be 145 thick.
I see 2 alternatives where the beam can be at the higher height and would like to know what you think of them, or if it can be solved in any other way.
- Use joist hangers on the beam to attach the rafters at the same height. It should (?) be stable, but perhaps not so nice to see the hangers.
Can you install the joist hangers "upside-down" so that the heel is not visible? Maybe with a few extra anchor screws?
Then I was thinking of possibly extending the roof on the other side of the beam, about 30 cm, I guess the same would apply there with joist hangers? - "Incorporate" the rafters into the beam using a half-and-half joint. I understand that it affects the bearing capacity of the rafters when you halve the thickness (even if only at the joint) but was thinking you might be able to reinforce right next to the joints with bolts and the beam could be reinforced with gusset plates?
Would 45x120 be sufficient as rafters?
If not, would it be enough with double 45x120 glued together?
I hope I make myself reasonably understood, otherwise, just let me know!
Best regards,
Christian
